Ham Radio: Low-Cost Gear

A brief discussion of low-cost ham radio equipment.


| September/October 1976



041-046-01

Copthorne MacDonald, inventor of slow-scan television.


PHOTO: MOTHER EARTH NEWS STAFF

Copthorne Macdonald is the inventor of slow-scan television ... a method of amateur radio transmission that allows ham operators to both hear and see each other during shortwave broadcasts.

Simple Gear

Martin Sample (WN6JTD) built the very neat station shown in the accompanying photo. While Martin did use a modular approach, he didn't put each of his modules in its own separate cabinet. Instead, he chose a single large, roomy aluminum box measuring 5-3/4" X 8" X 12" to house all the circuit board modules.

The unit pictured on the left contains the modules, while the one on the right houses Martin's transmitter amplifier. The receiver is of the simple direct-conversion type. This design approach allows a single variable-frequency oscillator (VFO) module to control both the receive and transmit frequencies. Thus, Martin's "bare mini mum" receiver requires only this VFO module—plus a "detector/audio preamp" circuit board—to produce enough audio output to allow one to listen to single sideband (SSB) and code (CW) signals with a headphone.

For better separation of CW signals Martin built a "CW filter" module, and to get loudspeaker volume he added an "audio output" board. These additional subassemblies fit right in the receiver cabinet, but of course they aren't needed if all you want to do is start listening on 'phones.

Sample's CW transmitter is simply a tube-type RF amplifier that boosts the output of the VFO module and keys it on and off. Transmitter output is about 45 watts, and the whole shebang is designed for 40-meter operation.

Incidentally, Martin powers his receiver with a 12-volt lantern battery, which he says has lasted for a year so far.





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